A charged particle beam writing apparatus writes a latent image having a predetermined shape onto a resist layer that is a base material of an etching mask or the like by irradiating a charged particle beam, such as an electronic beam. Since the charged particle beam writing apparatus can write the latent image with high resolution, the charged particle beam writing apparatus is used to produce an original pattern with high-resolution (also referred to as a reticle or a mask).
For example, when a latent image of a fine pattern is written onto the resist layer by a variable shaped beam type electron beam writing apparatus, figure allocation is performed, which enables construction of a planar shape of the latent image to be written by a combination of a plurality of figures using information on a cross-sectional beam shape and a cross-sectional size which can be shaped by the electron beam writing apparatus, and design data of the latent image to be written. Each of the figures used in the figure allocation has a shape and a size which enable writing by irradiating one shot of the electron beam or by sequentially irradiating a plurality of shots of the electron beam. Next, with respect to each of allocated figures, shot division to allocate one or a plurality of shots for writing a relevant figure is performed. Thereafter, a shot of which a gain or offset of the size needs to be corrected is extracted from all shots allocated through the shot division and a correcting step is performed to set a correction amount of the shot. Thereby, shot data indicating control information of an electron beam in the case of writing a latent image is generated. The electron beam is controlled according to the shot data so as to write the latent image of a fine pattern on the resist layer.
In order to increase writing precision of the latent image, a method of evaluating dimension precision of a charged particle beam has been already proposed. Also, a charged particle beam writing apparatus capable of increasing the writing precision of the latent image by resizing a predetermined shot has been already proposed.
For example, in the variable shaped beam estimation method disclosed in Japanese Laid-Open Patent Publication No. H09-186070, a plurality of rectangular patterns 1 having an identical dimension are prepared. At least one of these rectangular patterns is used for writing by a single electron beam shot, and the other rectangular patterns are divided by a line (deviation line) parallel to one side of the rectangular pattern to be used for writing by two electron beam shots. In the patterns obtained by a developing step after the writing step, a width of a pattern in the perpendicular direction to the deviation line is measured by a pattern dimension measuring apparatus. Then, the dimension accuracy of the variable shaped beam is estimated by examining a relationship between the measurement value of the pattern dimension, the presence or absence of the deviation line, or the position of the deviation line. According to this variable shaped estimation method, a displacement amount of a gain and offset can be accurately estimated, thereby a shot having a size equal to the maximum size or less can be shaped accurately.
In addition, Japanese Laid-Open Patent Publication No. 2012-114105 discloses a charged particle beam writing apparatus, which extracts a predetermined figure and resizes the figure in consideration of dimension variation upon figure allocation, in order to prevent a dimension of a fine pattern actually written in a resist layer from varying from a design dimension, due to a loading effect or the like which inevitably occurs when a developing step is performed to a latent image written on the resist layer.
For example, a photo mask is manufactured by writing a latent image of a fine pattern on a resist layer provided in a mask blank and by transferring the latent image onto a light shielding film of the mask blank using a charged particle beam writing apparatus. That is, the photo mask is manufactured by obtaining an etching mask by developing the resist layer in which the latent image is written, and by forming the fine pattern corresponding to the latent image with dry etching to the light shielding film of the mask blank through the etching mask. In this case, a manufacturing error in a dimension of the fine pattern formed in the light shielding film may be caused in the entire photo mask even though a shot in the charged particle beam apparatus is adjusted such that the latent image having desired dimension precision is written on a predetermined portion on the resist layer.
A manufacturing error value in an X direction of the fine pattern (i.e., a direction corresponding to an X-axis direction in a precision stage during the writing of the latent image) and a manufacturing error value in a Y direction of the fine pattern (i.e., a direction corresponding to a Y-axis direction in the precision stage during the writing of the latent image) are not uniform on the plane of the photo mask. On the plane of the photo mask, a difference between the manufacturing error value in the X direction and the manufacturing error value in the Y direction (hereinafter, referred to as an “XY dimension variation amount”) is inevitably changed by a formation position of the fine pattern. That is, distribution of the XY dimension variation amount occurs on the plane of the photo mask.
It is experimentally demonstrated that distribution of the XY dimension variation amount on the plane of the photo mask is changed depending on a material of the resist layer on which the latent image is written by a charged particle beam or a material of the light shielding film which is an underlayer of the resist layer. Also, it is experimentally demonstrated that, when the respective materials of the resist layer and the light shielding film are fixed, the distribution is changed according to a development condition in the case of developing the latent image written on the resist layer or a dry etching condition in the case of patterning the light shielding film using an etching mask generated from a photo resist layer on which the latent image is written. In addition, it is experimentally demonstrated that, when the respective materials of the resist layer and the light shielding film, and the development condition or the etching condition are fixed, reproducibility is observed in the distribution of the XY dimension variation amount between manufactured photo masks.
In this regard, it is estimated that the distribution of the XY dimension variation amount on the plane of the photo mask is caused by occurrence of distribution of angles at which the developer is introduced into the resist layer and distribution of directions in which the developer flows when the resist layer after writing of the latent image is developed, or is caused by interaction of spatial density distribution of plasma and flow of an etching gas, which occurs in the case of dry etching on the light shielding film using the etching mask generated from the resist layer after writing of the latent image.
Therefore, it is difficult to reduce the XY dimension variation amount in the fine pattern formed in the photo mask over the entire surface of the photo mask even though a shot having high dimension precision is formed by the charged particle beam writing apparatus and the latent image is written on the resist layer by using an evaluation result of an evaluating method disclosed in Japanese Laid-Open Patent Publication No. H09-186070. Similarly, it is difficult to reduce the XY dimension variation amount in the fine pattern formed in the photo mask over the entire surface of the photo mask although a predetermined figure is extracted in the case of figure allocation and the figure is resized as disclosed in JP 2012-114105 A.
An object of the present invention is to provide a charged particle beam writing apparatus that can reduce a XY dimension variation amount in a fine pattern formed by transferring a latent image onto a member to be patterned, over the entire surface of the member to be patterned when a latent image of a fine pattern is written onto a resist layer formed on the member to be patterned by a charged particle beam.
Another object of the present invention is to provide a charged particle beam writing method that can reduce a XY dimension variation amount in a fine pattern formed by transferring a latent image onto a member to be patterned, over the entire surface of the member to be patterned when a latent image of a fine pattern is written onto a resist layer formed on the member to be patterned by a charged particle beam.
Further another object of the present invention is to provide a shot correction method of a charged particle beam writing method that can reduce a XY dimension variation amount in a fine pattern formed by transferring a latent image onto a member to be patterned, over the entire surface of the member to be patterned when a latent image of a fine pattern is written onto a resist layer formed on the member to be patterned by a charged particle beam.